The invention consists of a clasp of the parrot type, equipped with an opening button, which is particularly indicated to join the ends of chains with which ornamental necklaces and bracelets are made so it is indicated for jewellery, silverware and costume jewellery in general.
There are known parrot clasps which are formed by an external shell, by a rotating lever and by an internal thrust spring. The external shell is equipped with a hooking cavity on the first end, with an ample cavity at the centre where the rotating lever and the internal thrust spring are lodged, and the other end is shaped like a hook. The rotating lever acts like a balance arm: one of its ends, shaped like an arm, interacts with the hook on the external shell, the other end protrudes from the said external shell and forms the activation tab.
Inside the cavity of the external shell there is the pin type thrust spring whose threadlike end branches, more or less of the same length, interact respectively with the external shell and with the rotating lever, constantly pushing the latter towards the closed position.
The above described parrot clasp is widely used because easy to use, and because when it is set on a bracelet or a necklace it is also attractive.
The inconvenience of said clasp is due to the fact that the tab which activates the rotating lever is very small and is usually activated by the user with the thumb nail therefore, when the internal spring is very hard, the user""s nail can break.
In order to avoid said inconvenience, which is considered seriously by those users who take good care of their nails and keep them long, clasps, similar to the parrot ones, have been created whose rotating element is not pulled but pressed to move it from the closed to the open position so that it is not easy to break ones nails when activating it.
One of said clasps, patented in the U.S.A. with U.S. Pat. No. 4,340,999, filed on Jul. 16, 1980, consists of an outer shell ending with a hook and of a rotating lever which is adequate to interact with the free end of said hook. Said lever is hinged on to the external shell towards one end and a portion of its central part is placed in view through a flared depression on the edge of the same external shell. Through said depression the user can push the lever and rotate it towards the open position, that is the position in which the free end of the lever is distant from the hook-shaped end of the external shell. Said clasp is therefore activated by means of a pressing action to be carried out with the finger nail or with the finger tip to push the rotating lever and therefore the clasp to its open position. The pressing action will be contrasted by the resistance carried out by the internal spring. Another clasp, this one also similar in shape as those of the parrot type, patented in the U.S.A. on Sep. 3, 1991 and granted with U.S. Pat. No. 5,117,539 also consists of an external shell, of a rotating lever and of the same type of internal spring. At one of its ends the external shell is equipped with a hooking hole, at its centre it is equipped with an ample cavity to lodge the internal spring and the rotating lever, the second end is shaped like a hook with which the rotating lever interacts to determine the closed position of the clasp. The external shell of this clasp is also equipped with two openings through which the ends of the rotating lever protrude outwards as this acts like a balance arm. One of its ends is shaped like an arm to interact with the hook shaped end of the external shell; the other end is instead shaped like a knee and juts out of the second opening of the shell. The user obtains the rotation of the rotating lever contrasting the resistance of the internal spring, by means of a pressing action exerted on the knee shaped end.
In this clasp the rotating lever, shaped like a balance arm, is constantly subject to the pressure exercised by the internal spring which pushes it towards the closed position and, when activated by an adequate pressure applied by the user on the thin jutting knee, it rotates to the open position.
The pressure applied by the user is practically superimposed to the resistance exercised by the internal spring. Therefore, in order to defeat the action of the latter the user is required to apply at least a pressure that is slightly higher than the action of said internal spring.
Given the much reduced size of the parrot type clasps and the thinness of the protruding knee of the rotating lever shaped like a balance arm, the activation of the latter is complex if a strong internal spring is used to ensure a satisfactory operation of the same clasp over a long period of time.
Finally, there is another known clasp, this one is also similar in shape to the parrot type ones, patented in the U.S.A. on Mar. 11, 1994, granted with U.S. Pat. No. 5,479,795, comprising an external shell terminating at one end with a hook-shaped protrusion and furnished at the other end with a U-shaped strip which creates the hooking cavity. The strip can also hold a diamond, whose rear tip passes through the external shell and acts like the rotation pivot for the rotating arm.
Said rotating arm is housed inside the external shell and its free end is still capable of interacting with the hook-shaped end of the same external shell. However, said rotating arm is furnished towards its middle with a tab that protrudes outside the shell, by pressing this tab the arm is made to rotate and therefore positions the clasp from the closed position to the opened one, this is contrasted by the internal spring. The rotating arm of said clasp operates like a lever with the fulcrum at one end, and towards the middle is pushed constantly to the closed position by the internal spring and pushed on the jutting tab by the user""s action when it must be opened. This clasp is shaped so that its rotating arm operates like a lever of the third type. It is therefore an inefficient lever since the user must exercise a much higher pressure against the resistance of the internal spring for it to open.
The known parrot type clasps, whether those with the protruding end of the rotating lever that require to be dragged, or those with the protruding end of the rotating lever to be activated by compression to position them in the open position, require external pressures that are higher than the resistance carried out by the internal spring. Therefore, when the internal spring is strong, to ensure the proper operation of said clasps over time, it also becomes difficult to take them from the closed position to the opened one. Said difficulty is considerable because the part on which the pressure must be applied to open the clasp is very thin, so it requires using ones finger nail and not the user""s finger tip to carry out its rotation.
The aim of the present invention is to create a clasp that is simple to construct so that it has a low cost, which has a parrot shape so that it is apropriate to be used on ornamental necklaces and bracelets, as well as being easy to modify in the external profile so that it can be adapted aesthetically for ornamental chains of varying shapes, without altering its functional logic. Another aim is to present a rotating lever that is appropriate to interact with the hook-shaped end of the external shell and which can be activated by a relatively small amount of pressure, even when a very strong internal spring is used. Another aim again is that of having a clasp that can be easily activated, which therefore presents a pressure point capable of being activated by the pressure of the users finger tip and which does not require the use of the corresponding nail, preserving it in this way from any type of pressure and therefore the danger of breakage.
The invention that has allowed to obtain said results consists of a clasp equipped with an external shell, that is molded or microfused, with a strong internal thrust spring and a rotating lever with a protrusion shaped like an activation button. At one end the external shell is shaped like a hooking bracket, towards the centre it is equipped with an ample internal lodging and at the second end it is shaped like a hook, while on one side, on the side to which its hook-shaped end converges, it has a long opening through which the activating button-shaped protrusion of the rotating lever emerges and on which the latter is allowed to rotate. The rotating lever therefore is furnished with a side protrusion shaped like a button, with a relatively large activation head, which facilitates its activation with the finger tip of the finger that pushes it. Said protrusion is also placed at a distance from the rotation fulcrum that is higher than that existing between said rotation fulcrum and the point on which the internal spring pushes with its reaction or resistance pressure. In this way the rotating lever acts like an efficient lever of the second type. Another advantage of the button shaped protrusion is due to the fact that when its head or bulge hits the containing shell, it also determines the open position of the clasp. The button-shaped protrusion also carries out an advantageous function due to its position in respect to the rotation action of the same lever and in respect to the point on which the internal resisting spring acts, since it allows the use of a very strong internal spring, which ensures the continuous function of the same clasp, even when the pressure required to open it is the same as that of the known clasps.